package com.sise.thread.Lock;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

/**
 * 作者：idea
 * 日期：2018/6/25
 * 描述：自己手写独占锁
 */
public class Mutex implements Lock {
    private final Sync sync=new Sync();
    private static class Sync extends AbstractQueuedSynchronizer{
        //显示是否处于占用的状态
        @Override
        protected boolean isHeldExclusively(){
            return getState()==1;
        }

        //尝试获取锁
        @Override
        protected boolean tryAcquire(int arg) {
            if(compareAndSetState(0,1)){
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

        //释放锁
        @Override
        protected boolean tryRelease(int arg) {
            if(getState()==0)
                throw new IllegalMonitorStateException();
                setExclusiveOwnerThread(null);
                setState(0);
                return true;
        }
            //返回一个condition队列
        Condition newCondition() {
                return new ConditionObject();
        }

    }


    @Override
    public void lock() {
        sync.acquire(1);
    }

    public boolean isLock(){
        return sync.isHeldExclusively();
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1,unit.toNanos(time));
    }

    @Override
    public void unlock() {
        sync.release(1);
    }

    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }

    public boolean hasQueuedThreads(){
        return sync.hasQueuedThreads();
    }
}
